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Subject: Bug in non-power-of-2 rings?
Date: Sun, 20 Aug 2023 11:07:33 +0200
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Thread-Topic: Bug in non-power-of-2 rings?
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Bruce Richardson" <bruce.richardson@intel.com>,
 <honnappa.nagarahalli@arm.com>, <konstantin.v.ananyev@yandex.ru>
Cc: <jerinj@marvell.com>,
	<dev@dpdk.org>
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Bruce, Honnappa, Konstantin,

Back in 2017, Bruce added support for non-power-of-2 rings with this =
patch [1].

[1]: =
https://git.dpdk.org/dpdk/commit/lib/librte_ring/rte_ring.h?id=3Db7446115=
5543430f5253e96ad6d413ebcad36693

I think that the calculation of "entries" in __rte_ring_move_cons_head() =
[2][3] is incorrect when the ring capacity is not power-of-2, because it =
is missing the capacity comparison you added to rte_ring_count() [4]. =
Please review if I'm mistaken.

[2]: =
https://elixir.bootlin.com/dpdk/v23.07/source/lib/ring/rte_ring_c11_pvt.h=
#L159
[3]: =
https://elixir.bootlin.com/dpdk/v23.07/source/lib/ring/rte_ring_generic_p=
vt.h#L150
[4]: =
https://elixir.bootlin.com/dpdk/v23.07/source/lib/ring/rte_ring.h#L502

-Morten